The present invention relates to a quiet valve or the like, and more particularly to a novel and improved arrangement for a series of orifices and expansion chambers in a fluid flow restrictor means to achieve an orderly and silent dissipation of fluid energy in a throttling process.
Fluid flowing at high velocities and under high pressure through a valve may cause objectionable noise problems and subject the valve structure to severe cavitation. These problems. are caused primarily by a sudden drop in the pressure as the fluid flows through the valve. Accordingly, many prior art devices have been proposed for utilizing a fluid flow restrictor means arranged intermediate the inlet and outlet of the valve to effect a controlled, multiple stage dissipation of the fluid energy. Typically, the fluid is caused to flow through labyrinthine paths or through a series of orifices and expansion chambers resulting in the gradual dissipation of energy either through multiple changes of direction, controlled and limited expansion, friction or a combination of these.
Representative of prior art valve constructions are the Parola U.S. Pat. No. 3,722,854, and the Kubota et al. U.S. Pat. No. 3,917,221. Each of these patents discloses a high pressure drop restrictor means wherein the fluid is passed through a multiplicity of expansion chambers and restricting orifices arranged in a series to effect an energy dissipation in multiple stages. The pressure drop at each stage is kept sufficiently low to avoid cavitation and the generation of excessive noise. Although the prior art proposals have been effective in greatly reducing the noise and cavitation problems, they have not been entirely satisfactory in that they comprise structures which are costly to manufacture, difficult to arrange according to precise engineering specifications, or both. Consequently, the prior art lacks a fluid flow restrictor which is conveniently adaptable to the exact requirements of a particular application, yet is capable of economical production.
It is a primary objective of the present invention to provide a novel and improved fluid flow restrictor for a high energy fluid valve or the like which is convenient and economical to manufacture and which is capable of achieving highly advantageous geometric relationships of orifice sizes and expansion chamber volumes. Generally, the invention comprises a flow restrictor means wherein a series of expansion chambers and orifices are formed by overlapping openings of close-fitting mating rigid parts. The openings are conveniently drilled in the mating parts and the parts are arranged in a contacting relationship relative to one another to achieve a predetermined overlapping relationship between the openings of contiguous parts. Each opening is uniform throughout the thickness of the individual part. The openings may be formed in any predetermined array over the surface of each of the mating parts and the mating relationship between the parts may be established to provide an overlap of predetermined dimensions between complementary openings. In this manner, the individual openings form expansion chambers, the volume of which is determined by the diameter of the opening and the thickness of the part. In a preferred arrangement, the thickness of the part is in the order of 1/2 to 1 times the dimension of the opening diameter. The restricting orifices for fluid communication between the expansion chambers are formed by the circular arcs of the overlapping openings. The dimensions of each orifice are determined by the opening size and the amount of overlap. Accordingly, the disclosed structure provides a novel flow restrictor which may be easily arranged according to precise engineering specifications for a particular application. All of the critical dimensions for the expansion chambers and orifices are determined by the size of the openings, part thickness and relative positions of the mating parts. These factors may be determined with great mathematical exactness and easily implemented into the structure of the present invention. Moreover, any number of mating parts may be arranged in series to provide any desired number of expansion chambers and orifices.
In accordance with a specific aspect of the present invention, the mating parts comprise close-fitting concentric cylinders arranged within a valve body between the inlet and outlet passages of the valve. A series of openings are formed in a desired pattern over the surface of each cylinder and the cylinders are shifted, one relative to the other to provide a predetermined overlapping relationship between the openings. Likewise, the opening sizes and cylinder thickness may be of any predetermined dimensions.
In one advantageous form of the invention, an axially movable valve plug is received within the interior of the innermost cylinder and is operable through a limited stroke to uncover the openings in a progressive manner to permit fluid flow. The openings may be aligned about a given point to form orifices of uniform dimensions or they may be arranged to form larger orifices in conjunction with increasing valve stroke, to provide a non-linear valve characteristic. In a preferred form of the invention, the openings are arranged in a helical pattern about the cylinder wall. As the valve plug is retracted to open the valve, several of the openings will be at various stages of being opened at any point in the stroke. This will afford a smooth, stepless flow characteristic in the opening of the valve.
In accordance with another specific aspect of the invention, the teachings of the present disclosure may be applied for use as a backpressure plate, for example, in a desuperheater outlet. In this embodiment, the openings are arranged at the vertices of equilateral triangles of predetermined dimensions across the surface of a plate, whereby the openings in successive close-fitting plates may intersect either one, two or three openings in a contiguous plate. This arrangement allows a high degree of mixing of the fluid which is desireable in a high pressure outlet.
For a better understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiments and to the accompanying drawings.